This invention relates generally to an electromagnetic clutch-brake unit which is selectively operable to either couple a rotatable driven element for rotation in unison with a rotatable driving element or to uncouple the elements and apply a braking force to one of the elements. Units of this general type are disclosed in British Pat. No. 1,166,180 and in U.S. Pat. Nos. 3,738,461 and 3,749,955 and comprise a selectively energizable electomagnetic coil adapted to effect shifting of an armature between clutching and braking positions. The armature is connected to rotate with one of the rotatable elements and, when shifted to its clutching position, the armature couples that element for rotation with the other element. When shifted to its braking position, the armature de-clutches the elements and coacts with a rotationally fixed braking member to effect positive braking of the one element.
The clutch-brake unit disclosed in U.S. Pat. No. 3,738,461 is of the so-called neutral type in that the unit can be operated so as to neither clutch nor brake the one rotatable element. When the unit is so operated, the one element may rotate freely or free-wheel relative to both the unit and the other rotatable element.